Technical Field
The present invention relates to a high-speed closing device which quickly grounds an electric circuit, at which a fault is caused, and can flow a fault electric current to the earth, or rapidly short-circuits between electric circuits, at which a fault is caused, and can detour and pass a fault electric current, when an electric fault, such as a ground fault or a short circuit, is caused in switchgear.
Background Art
An electric power receiving and transforming system is a facility system which is essential for a social infrastructure for an electric power supply and demand of a building, a factory or the like, and very high safety and reliability are required. Therefore, a process, in which safety and reliability are sufficiently considered for an overall procedure of a production step, installation work, operation, and maintenance, is used. However, there is very rare case in which an insulation function of an electrical circuit is lost and an accident fault, such as a ground fault or a short circuit, is caused by an intrusion of a small animal or a foreign material, which is not expected, an insulation deterioration by an aged usage, or instrument damage caused by an expected great earthquake.
In particular, when an internal short circuit fault of an enclosed device, such as switchgear, is caused, a large electric current arc is caused, and a plasma state at 10000° C. through 20000° C. is caused at a neighborhood of the arc, so that a neighboring metal or insulation material is partly evaporated. Moreover, a temperature of gas having an insulation capability, such as air neighboring the arc, is instantly raised at a high temperature, and the gas is expanded, and a pressure in the device is set as a very high pressure.
In general, a pressure discharging device is provided in switchgear or the like, and metal gas and insulation material cracked gas, which are evaporated within roughly 10 millisecond, and high pressure gas having an insulation capability, which is thermally expanded, are discharged to the outside of the device, whereby it is prevented that the switchgear is broken. However, when the fault is continued, the large electric current arc is continuously caused, so that a failure neighboring the arc in the device is increased.
An elimination of an electric fault, which is caused in the above-described electric power receiving and transforming system, is performed by using an electric power breaker which is provided in order to protect the electric circuit. However, the electric power breaker detects the fault and separates a failure electric circuit in accordance with an operation of the breaker, and roughly 100 millisecond or more time is required until the arc of the switchgear is removed. In the above-described case, damage of the power receiving and transforming system is large, and it is estimated that damage, by which a device cannot be recycled, is caused in the device which is a cause of the fault.
In order to counter the above-described problem, after an electric fault, such as a ground fault or a short circuit, is caused, there is a suggested method by which a fault electric current is detoured and passed to the earth within a very short time by using a grounding energization circuit having an impedance which is very lower than an impedance of a fault circuit, and there is a suggested high-speed closing device for using in the grounding energization circuit, by which an arc at a fault portion is disappeared within a short time, and a short circuit closing operation is performed within a short time (for example, refer to Patent Document 1 and Non-patent Document 1).
In a high-speed closing device which is described in Patent Document 1 and Non-patent Document 1, one contact is formed between phases of an electric circuit or between electrodes which connects the electric circuit and the earth. When one contact is formed, it is required that space of which insulation distance is wider than an insulation distance by which a discharge or the like is not caused between a contact of a movable contactor and a fixed contactor terminal, is maintained, and it is required that a wide distance between electrodes is maintained. When the wide distance between the electrodes is maintained, a shift distance of the movable contactor for connecting between the electrodes is extended, and a time length, until a short circuit and closing operation is performed, is extended. In order to counter the problem, there is a suggested high-speed closing device in which two contacts are formed between phases of an electric circuit or between electrodes which connects the electric circuit and the earth, and a distance between each of the electrodes is shortened, and a short circuit and closing operation can be performed within a short time (for example, refer to Patent Document 2).